C# in a Nutshell, Second Edition

Chapter 45. System.Xml.XPath

XPath is a W3C specification for locating nodes in an XML document. It provides an expression syntax that can determine a node based on its type, location, and relation to other nodes in a document. XPath is generally not useful alone, but works in conjunction with other tools, especially XSLT. Figure 45-1 shows the types in this namespace.

System.Xml.XPath provides types that evaluate expressions and match nodes in XML documents. XPathDocument is a document object designed to provide fast document navigation through XPath and is used by the System.Xml.Xsl classes for XSLT transformations. XPathNavigator is the core entry point for doing XPath expressions; it is abstract, allowing for more than just XML documents to be XPath-navigated. For example, an ADO.NET provider could, if it desired, implement the IXPathNavigable interface and return an XPathNavigator that translated XPath queries into a SQL SELECT statement. (See Aaron Skonnard’s MSDN Magazine article “Writing XML Providers for Microsoft .NET” for more details about using XML-based technologies over data sources other than XML documents.)